The invention relates to a planetary gear transmission with an variable transmission ratio, without a ring gear wheel, and comprising: a first sun gear arranged on a first operating shaft and at least one first planetary gear connectable thereto; a second sun gear arranged on a second operating shaft and at least one second planetary gear connectable thereto; planetary shafts, rigidly attaching each of the second planetary gears to one of the first planetary gears, in which case the first and the second planetary gears form first pairs of planetary gears, in which the planetary gears rotate at the same angular speed; and a planetary carrier that is common for the first and second planetary gears.
For instance from the publications WO-93/15337, WO-98/50715, there are known planetary gear transmissions that are compiled, in a conventional manner, of one sun gear, one series of correspondingxe2x80x94planetary gears and a ring gear wheel, so that the transmission ratio of their planetary gear transmissions can be adjusted for example by slowing down the ring gear wheel either mechanically or by means of a generator or a or hydraulic pump. According to both of said publications, the primary motor rotates the sun gear, and power is taken out of the gear arrangement to the target of usage from the planetary carrier. The publication DE-197 51 231 A1 describes a structure that in other ways corresponds to the ones disclosed in the above mentioned publications, but as an inverted arrangement, i.e. the power is brought into the planetary carrier of the gear transmission and it is taken out of the gear transmission to the target of usage from the sun gear. Here the ring gear wheel is slowed down by means of an AC inverter. The publications EP-0 748 953 A3 and GB-2 287 512 A describe somewhat different usages of a planetary gear transmission, although the planetary gear transmissions themselves represent exactly the same type as above. In said latter arrangements, the primary motor rotates the ring gear wheel, and the power is taken out of the gear transmission to the target of usage from the sun gear, whereas the transmission ratio is controlled by braking the planetary gears. In the above-described structures, the initial problem is the relatively small ratio of transformation, i.e. the difference between the largest and smallest transmissions, which is obtained by adjusting the speed of the ring gear wheel. For example in the publication WO-98/50715, the speed difference is said to be 2:1-3:1. In addition, in these structures a relatively large amount of energy is consumed in the braking of the ring gear wheel, which energy is removed from the power of the output shaft and requires, due to said large amount, as the papers teach, components that take up a lot of space and/or are heavy in structure. Another drawback is the complicated construction, especially in the case of the patent EP-0 748 953.
The publications DE-666 235, DE-38 06 292 and U.S. Pat. No. 4,406,178 introduce planetary gear transmissions without ring gear wheels, with a transmission ratio that can be steplessly adjusted. In these gear transmission arrangements, on the input shaft there is arranged a sun gear to which one set of planetary gears is connected, and on the output shaft there is arranged a second sun gear, to which the second set of planetary gears is connected. The planetary gears are non-rotatably connected to each other by means of axles attached with bearings to the rotary planetary carrier, in which case the planetary gears rotate at the same angular velocity. The transmission ratio of the planetary gear transmission is adjusted by braking the planetary carrier either by means of a friction brake, which is coupled either between the planetary carrier and the housing of the device or between the planetary carrier and the input shaft, or by arranging belt transmission between the planetary carrier and the input shaft. Also in these arrangements, the drawback is a fairly low ratio of transformation, i.e. the difference between the largest and the smallest transmission. Another drawback is a high loss of energy, which means that the efficiency of the suggested arrangements is low.
The object of the invention is to realize a mechanical gear transmission with a transmission ratio that can be variable of steplessly adjusted within a wide margin, while one or several of the transition ratios can be locked at a fixed value and again released according to the situation of usage. A second object of the invention is this kind of variable, mechanical gear transmission that achieves a minimal lossin efficiency. A third object of the invention is this kind of stepless mechanical gear transmission, where a stepless or sliding change in the transmission ration can be achieved by many different, alternative ways. Yet another object off the invention is this kind of gear transmission that is simple in structure and possibly small in size.
The object of the invention is to realize a mechanical gear transmission with a transmission ratio that can be variable or steplessly adjusted within a wide marginal, while one or several of the transmission ratios can be locked at a fixed value and again released according to the situation of usage. A second object of the invention is this kind of variable, mechanical gear transmission that achieves a minimal loss in efficiency. A third object of the invention n is this kind of stepless mechanical gear transmission, where a stepless or sliding change in the transmission ratio can be achieved by many different, alternative ways. Yet another object of the invention is this kind of gear transmission that is simple in structure and possibly small in size.
The above described problems are solved and objects achieved by means of a planetary gear transmission with a variable transmission ratio, without a ring gear wheel, comprising: a first sun gear arranged on a first operating shaft and at least one first planetary gear connectable thereto; a second sun gear arranged on a second operating shaft and at least one second planetary gear connectable thereto; planetary shafts rigidly attaching each of the second planetary gears to one of the first planetary gears, in which case the first and second planetyary gears form first planetary gear pairs, where the planetary gears rotate at the same angular velocity; and a planetary carrier common to the first and second planetary gears; and further comprising, as a combination one or several coupling means for taking out the whole rotary force or part thereof from the planetary gear transmission, and/or for feeding it into the planetary gear transmission, alternatively: either via said first or second operating shaft; or via the planetary carrier; and at least to a first mode, where the planetary carrier is locked to be stationary, and to a second mode, where the planetary carrier is freey rotable.
The above described problems are solved and the objects achieved by means of a special planetary gear transmission according to the invention, characterized by what is set forth in the characterizing part of claim 1.
Among the most important advantages of the invention is the possibility to reach an extremely high ratio of transformation, so that with one and the same gear, there can be easily and steplessly reached for instance transmission ratios within the range of 1:10-1:1 or even higher, if necessary. A second advantage of the invention is that only a slight amount of power is consumed in said adjusting of the transmission ratio, and according to a preferred embodiment of the invention, the power loss is made nearly nonexistent. A third advantage of the invention is the possibility to realize the planetary gear transmission, when necessary, in a form where one or several of the transmission ratios can during operation and according to the situation at hand be locked in a fixed position and again released to be variable by following a simple procedure. When locked in a fixed position, the planetary gear transmission according to the invention operates in principle in similar fashion as a gear transmission with a fixed transmission ratio, i.e. accurately and always with minimal power losses. However, the stepless planetary gear transmission according to the invention is extremely simple and secure in operation.